What’s it about? What does that title even mean? Having sat through all two hours of Planetarium, I’m still none the wiser. French director Rebecca Zlotowski’s film initially hints at a passionate drama, its intimate sound design conjuring an atmosphere of creepy eroticism. The sisters’ seances are all heavy breathing and ecstatic gasps; Andre’s visions of the unnamed figure in the leather jacket simmer with mystery and homoerotic tension. In terms of trajectory and deeper meaning, however, Planetarium’s obscurity soon becomes a nagging frustration. There’s a blank uneasiness between Portman and Depp – a kind of non-charisma akin to the comically dead-eyed turns in Napoleon Dynamite. Come to think of it, all the performances in Planetarium are dialled back to almost somnambulant levels. Depp seems withdrawn and out of sorts, even when her character isn’t thoroughly drunk at one of Andre’s upper-crust parties. Portman’s turn is similarly difficult to read, as though all her energies have been expended on learning her French dialogue. (Both Depp and Portman’s command of French admittedly sounds excellent, at least to this writer’s tin ears.) In one scene, Portman walks into a room full of actors and filmmakers, and the camera holds meaningfully on the profiles of each character, an incongruous electronic score rising in the background. Like so many moments in Planetarium, it just hangs in isolation, disconnected from the scenes around it. In one of its more arresting moments, Planetarium draws a parallel between movie-making and spiritualism: a movie is a ghostly, semi-permanent image of people and places who will one day be lost to history. That’s an intriguing notion, one briefly touched on in the superb horror cinema documentary American Nightmares, and one well worth exploring further. Yet Planetarium fails to focus on this or any of the other situations it sets up; instead, it drifts, zombie-like, to a muted and shrug-worthy conclusion. Planetarium makes its UK debut at the London Film Festival on the 14th October.